Iron sulfate

“ The washed sample is then fused in the usual way to determine the proportion of sulphur existing as iron pyrites. The distinction between sulphur present as sulphate and sulphide is of importance in the examination of coals intended for iron smelting, as the sulphates of the earthy metals are reduced by the gases of the furnace to sulphides, which pass into the slag without affecting the quality of the iron produced, while the sulphur of the metallic sulphides in the ash acts prejudicially upon the metal. ”

“ This device not only makes the cast iron much more uniform, but also removes much of its sulphur by a curious slow reaction. Many metals have the power of dissolving their own oxides and sulphides, but not those of other metals. Thus iron, at least highly carburetted, i.e. cast iron, dissolves its own sulphide freely, but not that of either calcium or manganese. Consequently, when we deoxidize calcium in the iron blast-furnace, it greedily absorbs the sulphur which has been dissolved in the iron as iron sulphide, and the sulphide of calcium thus formed separates from the iron. ”

“ Where beds of common iron pyrites occur, the iron sulphide is converted into sulphate by exposure to the oxidising influence of the air. The result is an acid sulphate of iron, which is leached out and neutralised by addition of more iron in the form of scrap. The neutral sulphate is crystallised out of the liquor, and calcined in a muffle furnace, the shade of the ultimate product being governed by the degree or duration of the roasting. ”

“ SULPHATE OF IRON. Also called “Green Vitriol” and “Green Copperas,” is a combination of sulphuric acid and oxide of iron, and may be made by putting iron filings or pieces of iron into a mixture of sulphuric acid and water, and when all action has ceased evaporating the liquid, and setting it by till crystals form—these are of a pale green color. The sulphate of iron of commerce is formed by exposing the iron pyrites found in the coal districts to the air till it falls to powder; water is then poured over this substance, and the fluid collected and evaporated. ”

“ Metallic sulphides when fused with an excess of nitre are completely oxidised. If the ore is rich in sulphur, some inert body (such as sodium chloride, or, better, sodium carbonate) is added to dilute the action. With pure sulphur, the action is so energetic as to cause an explosion, so that care should be taken. With burnt ores (incompletely calcined pyrites) , there is sufficient oxide of iron present to prevent too rapid action. ”

“ The sulphate of iron is the starting point in preparing all the compounds of iron which are used in medicine, and it is important therefore, to know how to separate easily the impurities which are contingent to this extremely cheap article of commerce. ”

“ It is largely used in the laboratory as a source of sulphuretted hydrogen. The hydrated sulphide is a black, insoluble substance, rapidly decomposed by exposure to the air. Proposed by Mialhe as an antidote to the salts of arsenic, antimony, bismuth, lead, mercury, silver, and tin, and to arsenious acid; more especially to white arsenic and corrosive sublimate. A gargle containing a little hydrated sulphide of iron will instantly remove the metallic taste caused by putting a little corrosive sublimate into the mouth. ”

“ Copper sulphate is nearly as active, and is followed by zinc sulphate and cadmium sulphate. Lead acetate and nitrate, in a one-percent solution, only delay decay, while it is prevented by the same strength of iron sulphide. ”

“ The sulphur may be present as sulphide or sulphate.
Arsenic.—Take 5 grams, and evaporate with nitric acid; dilute, add ammonia, pass sulphuretted hydrogen, and filter. [Pg 287]
To the filtrate add "magnesia mixture." Collect the precipitate, ignite with nitric acid, and weigh as magnesic pyrarsenate.
The following may be taken as an example of the composition of an impure black tin:—
Examination of Hardhead.—In the smelting of tin ores a quantity of speise, known as "hardhead," is produced. It is essentially an arsenide of iron, carrying a considerable quantity of tin. ”

“ The action of diluted sulphuric acid on metals closely resembles that of dilute hydrochloric acid. Magnesium, aluminium, iron, zinc, nickel, cobalt, manganese, and cadmium dissolve, with evolution of hydrogen, in the cold acid, or when warmed. The action of hot and strong sulphuric acid is [Pg 59] altogether different; it acts as an oxidising agent, and is itself reduced to sulphur dioxide or even to sulphur. The following metals are attacked in this way:—copper, bismuth, mercury, silver, antimony, tin, and lead. Gold, platinum, and arsenic are not affected. ”

“ The explanation is, that the waste pyrites 'contained not only sulphide of iron and earthy constituents, but also sulphide of zinc, and that by the influence of the oxygen of the atmosphere and the presence of water, these sulphides were gradually converted into the corresponding sulphates;' and these, continually extracted by the{751} rain-water, soaked into the soil, contaminated the wells, and produced other injurious effects.
The want of really efficient names to distinguish various kinds of manufactured iron has long been felt in the iron trade. ”

“ The effects of oxidation may be seen in the alteration of many kinds of rocks and in red and yellow colors of soils and subsoils.
Pyrite is a very hard mineral of a pale brass color, found in scattered crystals in many rocks, and is composed of iron and sulphur (iron sulphide) . Under the attack of the weather it takes up oxygen, forming iron sulphate (green vitriol) , a soluble compound, and insoluble hydrated iron oxide, which as a mineral is known as limonite. Several large masses of iron sulphide were placed some years ago on the lawn in front of the National Museum at Washington. ”

“ The residuary impure black oxide is mixed with as much sulphuric acid (concentrated) as will make it into a paste, which is exposed at first to a moderate heat, then to a cherry-red ignition for an hour. The sulphate thus obtained is reduced to powder, and dissolved in water. To the solution, carbonate of potash is gradually added, in order to separate the remaining portion of oxide of iron; the quantity of which depends upon the previous degree of calcination. If it be not enough oxidized, the iron is difficult to be got rid of. ”

“ The iron in water from old coal pits and shale deposits is usually present as sulphate due to the oxidation of pyrites, a sulphuret or sulphide of iron. Water from heaths and moorlands is often acid from certain vegetable acids termed "peaty acids." This acidity places the water in the condition of a direct solvent for iron, and that dissolved iron may cause great injury. If such water cannot be dispensed with, the best way is to carefully neutralise it with carbonate of soda ”

“ That's a good idea, Dave. I might use a sulphide—nearly all sulphides are colored, and form very easily and rapidly. Or I might use liquid ozone. That will tarnish almost anything to an oxide, which is also apt to be colored. I could certainly heat the ship that way, but I wonder—I'm afraid that the oxide or sulphide would break down too easily. There is only one metal that they might use on which that would work, namely steel. Iron sulphide is black, stable, and will not decompose readily. ”

“ Precipitation with sulphur dioxide and sulphuretted hydrogen proceeds much more rapidly, and has been adopted at many works. Sulphur dioxide, generated by burning sulphur, is forced into the solution under pressure, where it interacts with any free chlorine present to form hydrochloric and sulphuric acids. Sulphuretted hydrogen, obtained by treating iron sulphide or a coarse matte with dilute sulphuric acid, is forced in similarly. The gold is precipitated as the sulphide, together with any arsenic, antimony, copper, silver and lead which may be present. ”

“ Combined with metals (sulphides) , it is common in all mineral districts. Iron pyrites (FeS2) is the most abundant source of this element. Sulphates, such as gypsum, are fairly common, but have no value so far as the sulphur in them is concerned. In coal it exists as an impurity, occurring partly as a constituent of organic compounds.
Sulphur, whether free or combined with metals, forms, on burning, sulphurous oxide (SO2) , which by the action of oxidising agents and water is converted into sulphuric acid. ”

“ The fuel has, in addition to its duties of deoxidizing and carburizing the iron and yielding the heat needed for melting both the iron and slag, the further task of desulphurizing the iron, probably by the reaction FeS + CaO + C = Fe + CaS + CO.
The desulphurizing effect of this transfer of the sulphur from union with iron to union with calcium is due to the fact that, whereas iron sulphide dissolves readily in the molten metallic iron, calcium sulphide, in the presence of a slag rich in lime, does not, but by preference enters the slag, which may thus absorb even as much as 3% of sulphur. ”

“ Copper sulphide may be converted either into the sulphate, which is soluble in water; the oxide, soluble in sulphuric or hydrochloric acid; cupric chloride, soluble in water; or cuprous chloride, which is soluble in solutions of metallic chlorides.
The conversion into sulphate is generally effected by the oxidizing processes of weathering, calcination, heating with iron nitrate or ferric sulphate. It may also be accomplished by calcination with ferrous sulphate, or other easily decomposable sulphates, such as aluminium sulphate. Weathering is a very slow, and, therefore, an expensive process ”

“ When heated to the temperature of 560° F. it takes fire, burns away with a dull blue flame of a suffocating odour, and leaves no residuum. When more strongly heated, sulphur burns with a vivid white flame. It is not affected by air or water.
Sulphur is an abundant product of nature; existing sometimes pure or merely mixed, and at others in intimate chemical combination with oxygen, and various metals, forming sulphates and sulphurets. See Ores of Copper, Iron, Lead, &c., under these metals. ”

“ The result is a bluish colored mixture, soon changing to olive green. If the sulphate of iron be not properly selected, or if it be rubbed in the mortar, as inferred from the formula, the mixture is more or less brown and proportionably deteriorated. Of course, we should not “take sulphate of iron in powder.” {44}
In giving directions for making a compound, something, certainly, is to be expected from the knowledge and skill of the manipulator. ”

“ The presence of certain neutral salts, especially sodium chloride (common salt) , has a very marked influence on the destruction of iron [17] .
When iron filings are exposed to air and moisture, oxidation takes place; the action is, however, according to Krefting, far more intense in the presence of an alkaline chloride. A mixture of iron filings and sodium chloride exposed to moisture is converted in a few days into a black powder which has the following composition:—11·4% FeO, 80·0% Fe2O3, 8·6% H2O, thus resembling the “iron-black” of Lemery ”

“ Sulphur is now generally regarded as emanating from the stage of intermittent lethargy of a volcano, and the sulphides of iron, copper, arsenic, zinc, selenium, etc., fall in the same category as sulphur; they are secondary, not primary, formations. In the stage further off we have the host of sulphates produced by the oxidation of the sulphur into sulphuric acid, and its subsequent reaction on the metals and earths with which it becomes associated. ”

“ As it cools to the atmospheric temperature, beautiful crystalline needles form, which may be washed sufficiently with cold alcohol, or even tepid water. The usual impurities of the sulphur, which are carbonate and sulphate of zinc, oxide and sulphuret of iron, sulphuret of arsenic and silica, will remain unaffected by the volatile oil, and may be separately eliminated by the curious, though such separation is of little practical importance. ”

“ The value of limestone as a flux depends upon its freedom from impurities, such as silicon and sulphur.
Sulphur and phosphorus are two elements which must be kept out of the product. When there is too much sulphur, the iron is exceedingly brittle at a dull red heat, although it can be worked at a higher or lower temperature. It is called red-short iron and makes welding difficult. With steel, sulphur diminishes the tensile strength and ductility. If there is too much phosphorus combined with iron, the metal will crack when hammered cold. ”

“ When strongly heated iron inflames in oxygen and in sulphur vapour; it also combines directly with the halogens. It dissolves in most dilute acids with liberation of hydrogen; the reaction between sulphuric acid and iron turnings being used for the commercial manufacture of this gas. It dissolves in dilute cold nitric acid with the formation of ferrous and ammonium nitrates, no gases being liberated; when heated or with stronger acid ferric nitrate is formed with evolution of nitrogen oxides. ”

“ If exposed to a sudden, though gentle heat, by holding it, for instance, in a hand when that is warm, it will sometimes break in pieces with a crackling noise.
145It is a remarkable circumstance, that, if a bar of iron be heated to perfect whiteness, and then touched with a roll of sulphur, the two bodies combine, and drop down together, in a fluid state, forming what is called sulphuret of iron, a compound of the same nature as iron pyrites (236) . ”